class Calc:
    def mul(self, x,y):
        z=x*y
        return z
    def div(self,x,y):
        if y!=0:
           z=x/y
           return z
        else:
            print('除数为0')
            return 0
if __name__=='__main__': #main表示自己的意思
    c=Calc()
    r1=c.mul(10,20)
    print('相乘结果:',r1)
    r2=c.div(20,2)
    print('相除结果:',r2)